Method for roughening copper surfaces for bonding to substrates

Abstract

The invention is directed to a method and composition for providing roughened copper surfaces suitable for subsequent multilayer lamination. A smooth copper surface is contacted with an adhesion promoting composition under conditions effective to provide a roughened copper surface, the adhesion promoting composition consisting essentially of an oxidizer, a pH adjuster, a topography modifier, and a uniformity enhancer. A coating promoter may be used in place of the uniformity enhancer or in addition to the uniformity enhancer. The adhesion promoting composition does not require a surfactant. The process may further comprise the step of contacting the uniform roughened copper surface with a post-dip, wherein the post-dip comprises an azole or silane compound or a combination of said azole and said silane. The post-dip may further comprise, alone or in combination, a titanate, zirconate, and an aluminate. The pH adjuster is preferably sulfuric acid and the oxidizer is preferably hydrogen peroxide. A hydrogen peroxide stabilizer may be used in the adhesion promoting composition.

1 . A process for preparing roughened copper surfaces suitable for subsequent multilayer lamination, said process comprising the steps of: (a) applying a highly built alkaline cleaning solution to a copper surface to provide a substantially clean copper surface; and (b) dipping the clean copper surface into an adhesion promoting composition to provide a uniform roughened copper surface suitable for subsequent multilayer lamination, said adhesion promoting composition consisting essentially of an oxidizer, a pH adjuster, a topography modifier, and a coating promoter.  
   
   
       2 . The process according to  claim 1 , said adhesion promoting composition further consisting essentially of a uniformity enhancer.  
   
   
       3 . A process for increasing the adhesion of a dielectric material to a metal surface, wherein the metal surface comprises copper or copper alloys, said process comprising: 
 (a) contacting the metal surface with an adhesion promoting composition comprising an adhesion-promoting effective amount of: 
 (1) an oxidizer;  
 (2) an acid;  
 (3) a topography modifier; and  
 (4) a coating promoter;  
   (b) bonding the dielectric material to the metal surface which has been contacted with said adhesion promoting composition.    
   
   
       4 . A process according to  claim 3  wherein the adhesion promoting composition further comprises a uniformity enhancer.  
   
   
       5 . A process according to  claim 3  wherein the topography modifier is a 5-membered aromatic fused N heterocyclic compound, wherein the N heterocyclic ring has a nitrogen atom at position 1 bonded to a hydrogen atom.  
   
   
       6 . A process according to  claim 3  wherein the coating promoter is a 5-membered aromatic fused N-heterocyclic compound with 1 to 3 nitrogen atoms in the fused ring, wherein none of said nitrogen atoms are bonded to a hydrogen atom.  
   
   
       7 . A process according to  claim 3  wherein the coating promoter has the following structure:  
     
       
         
         
             
             
         
       
     
     wherein R1 is selected from the group consisting of hydroxyl groups, amino groups, alkyl groups, hydroxyalkyl groups, aminoalkyl groups, nitroalkyl groups, mercaptoalkyl groups, and alkoxy groups.  
   
   
       8 . A process according to  claim 3  wherein the coating promoter is 1-hydroxybeznotriazole.  
   
   
       9 . A method of preparing a printed circuit board for subsequent multilayer lamination, comprising the steps of: 
 (a) providing a printed circuit board, said printed circuit board comprising an imaged layer of copper bonded to a dielectric substrate; and    (b) contacting said imaged layer of copper with a surface roughening composition comprising: 
 (1) an oxidizer;  
 (2) an acid;  
 (3) a topography modifier, wherein said topography modifier is a 5-membered aromatic fused N-heterocyclic ring compound, wherein the N-heterocyclic ring has a nitrogen atom at position 1 bonded to a hydrogen atom; and  
 (4) a coating promoter having the following structure:  
                     wherein R1 is selected from the group consisting of hydroxyl groups, amino groups, alkyl groups, hydroxyalkyl groups, aminoalkyl groups, nitroalkyl groups, mercaptoalkyl groups, and alkoxy groups;    
 wherein the surface of said imaged layer of copper is roughened by said contacting step.  
   
   
   
       10 . The method of  claim 9 , wherein said surface roughening composition further comprises a copper salt.  
   
   
       11 . The method of  claim 9 , wherein said contacting step takes place in a tank having stainless steel surfaces.  
   
   
       12 . The method of  claim 11 , wherein said surface roughening composition further comprises a copper salt, wherein said copper salt protects said stainless steel surfaces from chemical attack.